Vactec vactrols vs. Smallbear's workalikes -- some observations and questions

[midwayfair]

First, I am by no means saying that there's anything wrong with the workalikes. I buy them all the time and have used them in several projects and almost every time they work great.

The LDR side in the 5C1 and 5C3 clones, by every metric I've been able to measure them, is basically identical.

I HAVE, however, noticed a kind of weird difference. It's in the LED side. Essentially, the LED in the Macron clones works just like a normal superbright LED. The forward voltage is pretty much spot on to a white LED, and it seems to draw the same amount of current.

The VTL5C1s have the biggest noticeable difference. They seem to require less current limiting to get to their brightest point. The measured forward voltage is ... higher than a green LED but lower than a blue LED, at least on the few I have left here. (I used to have dozens, but I used them all!) I got just under a 3V drop on mine.

The result is that under some circumstances, when the ON resistance is critical, just dropping in the Macron to replace the Vactec part might require an adjustment. In the circuit I was messing around with, I got a lower on resistance with the macron but higher dark resistance with the vactec under the same conditions. Extremely similar after testing three of each (so they're also very consistent).

I'm not too keen on cutting open a few $8 parts to see what's inside, but I wonder if anyone has any insight into this, or if anyone's observed something similar.

I'll be xposting this, so if I hear anything else where I'll let people know.

[flanagan0718]

+1 on this. I would love to know the differences on these as well. What led's they use, what the distance is, so on and so forth. I was debating on biting the bullet and ordering the Vactec and Silonex and cutting them open myself.

[RobA]

A couple of years ago, I did some comparisons between the VTL5C parts and the NSL parts and saw something similar. I didn't measure the forward voltage drops of the LED's. I just took some V vs R measurements for various different current limiting resistors. I didn't keep very detailed notes, but I do have this line in the file, "NSL-32SR3 requires much lower on current than the VTL5C2."

I don't know what LED's they are using in each of these, but the spec sheets for all of them claim similar forward voltages. They do spec the voltages at relatively high currents though. The doc for the VTL5C1 does have a plot of forward current versus forward voltage. Here's links to each of the spec sheets,
http://www.alliedelec.com/images/products/datasheets/bm/PERKINELMER/70219695.pdf
http://www.alliedelec.com/images/products/datasheets/bm/SILONEX_INC/70136790.pdf
http://www.macron.com.hk/images/mi1210cl-r.pdf
There's a doc available for the VTL5C parts that details and measures pretty much everything for them, but I don't have a link for it at hand.

After the price dropped on the VTL5C parts, I stopped looking at the others as replacements, so I didn't do any more research. I have a couple of each of the Macron parts around still and I should sit down and do a comparison of them against the other two spec wise.

[GermanCdn]

Actually, I was just going to post something very similar, so here's my findings.

Built up two Cardinals and Two MPJrs, one each with work alikes, and one each with real Vactrols.  Night and day difference. 

The MPJr with the workalike has barely audible modulation, you can hear when you twist the knobs while playing, but it really doesn't come to the party.  Figured I'd done something wrong and I had a spare board so I built up another one with real Vactrols.  Thick, rich modulation, makes you want to yak if you crank up the depth and back off the rate.  Completely different pedals with one part difference.

Same thing with the Cardinal.  I built up the first one with a couple of SB work alikes, and it did it's thing, but there was barely a noticeable difference between the modes on the switch.  Sounded "good enough" to box, and played on with it.  Also had a couple of spares, and since I'd built the first one as a four knob, I built the second one as a three knob with real Vactrols.  Again, completely different pedal, modes are distinct, it doesn't sound like "every other" trem pedal out there, etc, etc.  The one thing I did find with the Vactrols is that the Depth pot needed to be a 1kC as opposed to a 1kB, as the 1kB real effective sweep was between 1 oclock and 4 oclock.
So, long story short for me - I won't be buying anymore work a likes.  Don't sound the same.

Once I get the second Cardinal boxed up, maybe I'll shoot a vid of both of the Cardinal builds and both of the MPJr builds to compare the parts.  Again, if it only had happened once, I'd assume I'd made a mistake, however, if the same kind of things happen in two different circuits with two different LDRs...

CORRECTION - I pulled one of the LDRs in the Cardinal circuit, and it was in fact a Vactec unit, just a different batch then the second one I built from.  So I can't conclusively say that Macrons won't work in the Cardinal circuit, but they certainly underperformed in the MPJ.

[midwayfair]

Curtis, since you have that cardinal built up with the work-alikes, would you be willing to experiment with R16, R17, and R18? Try raising those. I'd do it myself, but my breadboards are currently occupied.

[GermanCdn]

Absolutely.  Will give it a shot this weekend and let you know.